I got ours from Amazon as well. Almost a year later and we're still at box #1! I don't use CS for regular laundry so I can't comment there. Haven't had any issues with CS...no detergent build up that I'm aware of. We somewhat hard water (we do have a whole house softener) which I think is contributing to the MF stinkies from minerals build up or unless it's the super saturated toddler pee!

I dissolve in hot water first and pour directly into the washer. We have a HE FL. Cold soak, hot wash with detergent and an extra rinse at the end. May run another normal cycle if I have a large load to ensure that the dipes are thoroughly rinsed. Hang to dry.